1. Field of the Invention
The present invention relates to a method of preventing polymer scales from sticking on the inner wall, etc. of a polymerization vessel during the polymerization of a monomer having an ethylenically double bond.
2. Description of the Prior Art
In processes of preparing polymers by polymerizing monomers in a polymerization vessel, known to arise is the problem that the polymers stick on the inner wall, etc. of the polymerization vessel in the form of scales. Once the scales of polymers stick on the inner wall, etc. of the polymerization vessel, the disadvantages may result such that the yield of the polymers and the cooling capacity of the polymerization vessel are lowered, the sticked scales of polymers may peel to mix into manufactures to bring about a lowering of the quality of manufactured polymers, and also much labor and time are required to remove the scales of polymers.
As methods of preventing polymer scales from sticking on the inner wall, etc. of a polymerization vessel, there have been hitherto proposed, for example, a method in which a polar compound, a dye, a pigment or the like is coated on the inner wall (Japanese Patent Publication (KOKOKU) No. 30343/1970 and No. 30835/1970), a method in which an aromatic amine compound is coated (Japanese Unexamined Patent Publication (KOKAI) No. 50887/1976), and a method in which a reaction product of a phenolic compound with an aromatic aldehyde is coated (Japanese Unexamined Patent Publication (KOKAI) No. 54317/1980).
These are effective in preventing polymer scales from sticking, when vinyl halide monomers such as vinyl chloride or monomer mixtures mainly comprised of said vinyl halide monomers and containing a small amount of monomers copolymerizable therewith are polymerized.
However, in instances in which the monomers to be polymerized comprise other monomers having an ethylenically double bond such as styrene, alphamethylstyrene, acrylate and acrylonitrile, these monomers have so large a dissolving power against coatings formed by the above sticking-preventing methods that part or the whole of the coatings may be dissolved away, so that it becomes impossible to effectively prevent polymer scales from sticking on the inner wall, etc. of a polymerization vessel.